JPH0515195A - Motor controller and control method - Google Patents

Abstract

PURPOSE:To provide a motor controller and control method for rotary driving a motor at high speed with low noise and low cost. CONSTITUTION:A switching element 107 for turning power supply 112 to a motor 105 ON/OFF is disposed between the motor 105 and the power supply 112, and the duty ratio of switching signal for the switching element 107 is modified at or within the output period of exciting signal for the motor 105.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control method and device for rotating a motor by switching the excitation phase of a motor such as a stepping motor, and more particularly to a motor control method and device having a plurality of operation modes, that is, ramp up / down and ramp up / down. The present invention relates to a motor control method and device for performing constant speed driving, holding operation, and the like.

[0002]

2. Description of the Related Art As a system for driving a stepping motor to rotate, a constant voltage drive system and a constant current system are the most commonly adopted systems. The former constant voltage drive system is widely used because it has a simple circuit configuration and is inexpensive. However, when the rotation frequency of the motor increases, the rise of the current in the motor winding is delayed due to the influence of the inductance of the motor winding. Therefore, when high-speed rotation driving is performed, the torque of the motor is reduced, and there is a problem that high-speed rotation cannot be performed. In the latter constant current drive method, the voltage and winding inductance are set so that the time constant of the motor winding is reduced, and the detected current value is detected while detecting the current value of the motor winding. This is a method in which a switching element such as a transistor turns on / off the current to keep the current value flowing through the winding constant.
According to such constant current driving, high-speed rotation of the motor can be realized, but on the other hand, there is a problem that the circuit configuration becomes complicated and the cost increases. Further, when driving the stepping motor, vibration of the motor occurs at the time of switching the phase excitation, so that noise is generated when the driving rotational speed of the motor is changed while keeping the current value constant. Therefore, it is necessary to change the constant current value to a current value suitable for the number of rotations of the motor, and there is a problem that a circuit for that is further required.

[0003]

Further, as a more advanced motor drive system, an encoder capable of detecting a small rotation angle less than the minimum drive step angle of the motor is attached to the rotary shaft of the motor, and a signal from the encoder is attached. In other words, there is known a control method in which the excitation phase is switched in synchronization with the rotation of the motor, the voltage or current is chopped, and the rotation speed of the motor is changed according to the duty. According to this method, the excitation phase can be appropriately switched even when the rotation speed of the motor changes. As a result, the so-called step-out state does not occur, and the rotation frequency becomes according to the electric power supplied to the motor winding, so that noise generation can be suppressed. However, according to this method, the number of parts that make up the drive circuit, including the encoder mounted on the motor rotary shaft, is the maximum compared to the constant voltage or constant current method described above, and the cost is high overall. There was a drawback that it became.

The present invention has been made in view of the above-mentioned conventional example, and an object of the present invention is to provide a motor control method and device capable of rotationally driving a motor at low cost and at high speed, and of rotating the motor with low noise. .

[0005]

In order to achieve the above object, the motor control device of the present invention has the following configuration. That is, a motor control device that outputs an excitation signal of a motor to drive the motor to rotate, the power supply supplying electric power to the motor, and the power supply to the motor provided between the power supply and the motor. Switching means for turning on / off the power supply, signal output means for outputting a switching signal of the switching means at an instructed duty ratio, output cycle of the excitation signal of the motor, or the signal output means within the cycle. Control means for instructing to change the output duty ratio of.

In order to achieve the above object, the motor control method of the present invention includes the following steps. That is, a motor control method for outputting a motor excitation signal to drive the motor to rotate, which is a switching signal for switching on / off the power supply to the motor within the switching timing of the excitation signal of the motor or the switching timing cycle. Change the duty ratio of.

[0007]

In the above structure, the switching means for turning on / off the power supply to the motor from the power supply is provided between the motor and the power supply for supplying the electric power to the motor, and the switching signal of the switching means is instructed. The duty ratio is output. The duty ratio of the switching signal is changed within the output period of the motor excitation signal or within that period.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a schematic configuration of a motor drive circuit of this embodiment.

In FIG. 1, reference numeral 1 denotes an MPU such as a microprocessor for controlling the rotation of a motor, which comprises a RAM 121 used as a work area and a ROM 122 storing a control program for the MPU. 1
02 is a PWM (Pulse Width Modurato)
r) unit (hereinafter referred to as a PWM unit), which is connected to the MPU bus, can output a pulse signal by setting its output frequency and duty according to an instruction from the MPU 101. An output port 103 is connected to the bus of the MPU and is synchronized with the phase switching signal output from the MPU 101 to synchronize the phase excitation signals (A to A) of the stepping motor 105.
D) is output. A programmable timer 104 starts clocking according to an instruction from the MPU 101, and when the instructed time has elapsed, the MPU 101 can be notified by, for example, an interrupt or a control signal.

Reference numeral 105 denotes a two-phase unipolar stepping motor. Reference numeral 106 denotes a transistor array, which turns on / off a corresponding transistor in response to a phase excitation signal output from the output port 103 to excite each phase of the stepping motor 105. 107 is a PNP transistor for current control, which is used in the PWM unit 10
A signal obtained by inverting the output pulse of 2 in the inverter 111 is input to control the winding current flowing in the stepping motor 104. 108 is a flywheel diode,
When the current control transistor 107 is turned off, it forms a current path for passing a current due to the counter electromotive force generated in the coil of the stepping motor 105. Reference numeral 109 denotes a diode for preventing a reverse current, which prevents a reverse current due to an induced voltage in the coil when the coil of the stepping motor 105 is energized. Reference numeral 112 is a power supply that supplies electric power to the motor 105.

FIG. 2 is a diagram showing the timing when the stepping motor 105 is rotationally driven by two-phase excitation.

The MPU 101 generates from the output port 103 excitation signals A to D necessary for driving the two-phase excitation of the stepping motor 105. The timing at which these excitation signals are switched is based on the timing of the timer 104, and is controlled under the software control of the MPU 101. By changing the time interval for switching the excitation phase, acceleration, constant speed, deceleration of the stepping motor 105,
Control of each mode such as slow speed is performed. Also MPU10
1 instructs the PWM unit 102 to output a constant frequency pulse, for example, a frequency pulse of 20 KHz or higher, which is higher than the audible range of the human ear, and corresponds to each mode such as acceleration, constant speed, and deceleration. It is instructed to output the pulse signal with a predetermined duty.

FIG. 3 is a diagram showing the relationship between the output waveform example of the signal 110 output from the MPU 101 to the PWM unit 102 and the speed of the stepping motor 105.

The duty of the signal E shown in FIG. 2 is determined by the PWM unit 10 when the signal 110 is as shown in FIG.
It corresponds to when applied to 2. And signal 110
The higher the signal level, the higher the duty ratio, and the lower the signal level, the smaller the duty ratio, and the shorter the time the signal is on.

When the signal output from the PWM unit 102 becomes high level in this way, the current control transistor 107 is turned on, and the current from the power supply is supplied to the stepping motor 105. Further, when the current control transistor 107 is turned off, the electric power stored in the inductance of the motor winding at the time of turning on is discharged through the flywheel diode 108. By repeating such operations, the stepping motor 1
The current flowing through the winding No. 05 is switched, and a current value proportional to the pulse duty of the output of the PWM unit 102 flows to rotate the motor.

In FIG. 3, a is a holding mode, b is a ramp up mode, c is a constant speed mode, d is a ramp down mode, e is a high speed ramp up mode, f is a high speed constant speed mode, and g is a high speed ramp. The down mode, h is the holding mode, i is the slow speed mode, and j is the holding mode.

The PWM value required when the stepping motor 105 rotates at a certain frequency is the power supply voltage, the inductance and resistance value of the winding of the stepping motor 105,
Furthermore, it depends on the load of the motor. Therefore, if the variation of these elements is within the predetermined range, a value considering the minimum variation of the power required in each mode can be set in advance as the set value of the PWM unit 102.
The load of the stepping motor 105 differs for each period of acceleration, constant speed, deceleration, and the like. That is, higher power is required during high speed operation than during low speed operation. Therefore, in this embodiment, the stepping motor 10
By outputting a pulse signal having a duty corresponding to the load of No. 5 from the PWM unit 102 and inputting it to the transistor 107, electric power required to operate the stepping motor 105 can be supplied. Therefore, the stepping motor 105
Of the stepping motor 1 with a torque according to the load without step-out and without applying more power than necessary.
05 can be rotated. As a result, it is possible to reduce noise when the stepping motor 105 rotates. <Second Embodiment> In the first embodiment described above, the PWM output value is changed every time the motor is rotated by one step as shown in FIG. 2, but the present invention is not limited to this. It is also possible to change the PWM value within one step driving of the motor.

FIG. 4 is a block diagram showing the structure of a motor drive circuit for performing such control. The parts common to the circuit of FIG. 1 described above are designated by the same reference numerals, and their description will be omitted. 4, in addition to the circuit configuration shown in FIG. 1, a terminal that can set a PWM value for each winding is added. The PWM unit 102a in FIG. 4 can output two types of pulse signals (switching signals) indicated by E and F in accordance with the signals 110E and 110F given from the MPU 101.

FIG. 5 shows the excitation signals A, B, C, and
FIG. 7 is a diagram showing output timings of D and switching signals E and F. The switching signals E and F determine the electric power applied to each winding, that is, the duty of PWM.

In FIG. 5, the PWM duty of the switching signals E and F is alternately increased immediately after the switching of the excitation phase of the motor, and when one of the duty ratios is increased, the other duty ratio is decreased. By doing so, it is possible to drive the motor so that the winding current of the motor rapidly rises and is then maintained at a constant value. It should be noted that such a switching timing of the excitation phase is determined by the timer 104.
It is based on the timekeeping by. Such control is particularly effective when motor torque is required at high rotation speed.

Although FIG. 5 shows only the period of four steps, smooth motor rotation can be obtained by changing the PWM duty for each step when ramping up, etc. It is the same. If the motor rotation speed further increases, the counter electromotive force works and the winding current does not flow easily. Therefore, the PWM duty switching time may be changed according to the motor rotation speed. <Third Embodiment> In general, since the stepping motor inevitably moves step by step, vibration occurs during rotation, resulting in noise. Particularly, noise is a problem when a motor that requires high-speed rotation is rotating at low speed. At this time, the rise time of the winding current was sufficiently faster than the step switching time, so excessive torque was produced, which was one of the causes of noise. In order to avoid such vibrations, conventionally, the method of switching the motor drive voltage was used to slow down the rise of the winding current to reduce noise, and there was a drawback that the number of circuit components increased. In addition, as a method for reducing noise and improving resolution by another method, double 1-2 phase, double double 1-2
Although a driving method of phase and the like is known, it can be easily realized by the method of this embodiment.

FIG. 6 shows an example of control waveforms when double 1-2 phase excitation is performed in the motor control circuit having the circuit configuration shown in FIG. Here, based on the measured value of the timer 104, simply set the PWM value to 1 / of the step interval.
Double 1-2 phase drive can be easily realized only by controlling in the cycle of 4. Further, a method is known in which the excitation signal of the motor is converted into a sine wave so that smoother motor rotation can be obtained. It is also possible to further divide such double 1-2 phase PWM value change timing and set it as a pseudo continuous sine wave signal.

As described above, particularly when the frequency is low, by adding to the drive current, smooth and low noise operation can be realized. <Fourth Embodiment> FIG. 7 is a block diagram showing the structure of a motor drive circuit according to a fourth embodiment of the present invention. The parts common to those in FIG. 1 are designated by the same reference numerals, and their description will be omitted.

In FIG. 7, an A / D converter connected to the MPU bus 71, and a temperature detecting element 72 such as a thermistor arranged in the equipment, detects the temperature in the motor drive circuit.

In this configuration, the MPU 101b outputs the excitation signal or when the motor 105 is started,
By inputting the resistance value of the thermistor 72 converted into digital information by the A / D converter 71, the ambient temperature is detected and stored. Based on the detected temperature, the duty ratio from the PWM unit 102 for turning on / off the electric power of the motor 105 described in the first embodiment is changed. This refers to the duty table stored in the MPU 101b to obtain the duty ratio corresponding to the temperature. This table is set so that the duty ratio is large when the temperature is low and small when the temperature is high. Therefore, since the torque becomes high at low temperature, it becomes possible to drive with sufficient torque even if the load increases. As a result, the motor rotates without step-out, and unnecessary torque is not applied to the motor when the temperature is high. Therefore, it is possible to suppress the temperature rise of the driver part and reduce unnecessary power consumption. Become.

FIG. 8 is a flow chart showing the control processing of the MPU in the above-mentioned embodiment, and the control program for executing this processing is stored in the ROM of the MPU.

When the rotation of the motor is instructed, the signal 110 is first output in step S1 and the PWM unit 102 is output.
Is set to output a pulse signal with a predetermined duty ratio. Next, in step S2, the time value is set in the timer 104. As a result, the excitation interval of the motor 105 is measured by the timer 104. Then step S3
Then, the excitation signals A to D are output via the I / O port 103, and the motor 105 is rotationally driven, for example, 1-2 phase excitation or 2-phase excitation.

Next, in step S4, the timer 104
Checks the set time to see if it has timed out, and if timed out, the process proceeds to step S5, where the motor 105 is rotated by a predetermined number of steps, and the motor 10
Check if the driving of 5 is completed. When the rotation of the motor 105 is not completed, the process proceeds to step S6, the table stored in the ROM of the MPU is referred to, and the signal 110 instructing the next duty ratio is output. This makes it possible to change the duty ratio of the PWM signal each time the excitation phase of the motor 105 is switched, as shown in FIGS. 2 and 5, for example.

At this time, the signal from the A / D converter 71 of FIG. 7 is input, and the signal 110 for setting the duty ratio according to the temperature at that time is output to thereby output the signal from the fourth embodiment. The operation of can be realized.

Next, in step S7, a time value indicating the next excitation interval is output to the timer 104. By gradually shortening this time value, the motor 105 can be acceleratedly driven, by gradually lengthening it, the motor 105 can be decelerated, and by making it constant, the motor 105 can be driven at a constant speed. In this way, the process proceeds to step S3 again, and the excitation signal is output to rotate the motor.

In this way, the motor 105 is rotated by the required number of steps, and when the driving of the motor 105 is completed, the process proceeds from step S6 to step S8, and the motor 105 is placed in the holding mode. Then, the PW is set so as to output the PWM signal having the duty ratio according to the holding mode.
Instruct the M unit 102.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. It goes without saying that the present invention can also be applied to the case where it is achieved by supplying a control program for executing the processing defined by the present invention to a system or an apparatus.

As described above, according to this embodiment, the motor can be rotated at a higher speed as compared with the constant voltage drive, and a circuit structure simpler than the constant current drive, that is, an inexpensive circuit can be realized. Is. Further, power setting according to the load can be realized by simply changing the PWM duty ratio. Therefore, it is possible to efficiently supply the electric power required for the motor operation and to rotate the motor without giving unnecessary electric power, so that the noise at the time of motor rotation can be reduced and at the same time, low power consumption can be realized. it can.

Further, as an application of this embodiment, scanning drive of a carriage used for horizontal scanning in a serial printer or the like is conceivable. Especially, in an apparatus using a bubble jet head, it can be combined with a small size and at a low cost. It is possible to realize a printer with high speed, low cost, low noise, and low power consumption.

Further, although not described in this embodiment,
It is also possible to reduce the cost by integrating the driver unit shown in FIGS. 1 and 4 into an integrated circuit and further reducing the mounting area. Further, in the above-mentioned embodiment, all the motors are explained as unipolar drive, but it goes without saying that bipolar drive is also possible.

[0037]

As described above, according to the present invention, the motor can be rotationally driven at low cost and at high speed, and the motor can be rotationally driven with low noise.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a motor drive circuit according to a first embodiment.

FIG. 2 is a timing diagram of an excitation signal and a PWM signal of each phase.

FIG. 3 is a rotational speed of the motor and PW in the first embodiment.
It is a time chart which shows the relationship with the signal to M unit.

FIG. 4 is a block diagram showing a configuration of a motor drive circuit according to a second embodiment.

[Figure 5]

FIG. 6 is a timing chart showing the relationship between the motor excitation signal and the PWM signal in the second and third embodiments.

FIG. 7 is a block diagram showing a configuration of a motor drive circuit according to a fourth embodiment.

FIG. 8 is a flowchart showing the operation of the MPU of this embodiment.

[Explanation of symbols]

71 A / D converter 72 Thermistor 101, 101a, 101b MPU 102 PWM unit 103 output (I / O) ports 104 timer 105 stepping motor 106 transistor array 107 Current control transistor 108 Flywheel diode 109 Reverse current prevention diode 112 power 121 RAM 122 ROM

Claims (3)

[Claims] 1. A motor control device that outputs an excitation signal of a motor to rotationally drive the motor, comprising: a power supply for supplying electric power to the motor; and a power supply provided between the power supply and the motor. Switching means for turning on / off power supply to the motor; signal output means for outputting a switching signal of the switching means at an instructed duty ratio; and an output cycle of the excitation signal of the motor, or within the cycle. A motor control device comprising: control means for instructing to change the output duty ratio of the signal output means. 2. A temperature detecting means for detecting an environmental temperature is further provided, and the control means changes the duty of the switching signal according to the environmental temperature detected by the temperature detecting means. The motor control device according to claim 1. 3. A motor control method for outputting a motor excitation signal to rotationally drive the motor, wherein the power supply to the motor is turned on at the switching timing of the excitation signal of the motor or within the switching timing cycle.
A motor control method characterized in that a duty ratio of a switching signal to be turned off is changed.